The present invention relates to a seal structure for sealing between an engine block and a cylinder liner in an internal combustion engine, especially a compression ignition type internal combustion engine.
In the manufacture of engine blocks, particularly for diesel engines, the engine block is normally cast with relatively loose tolerances. In order to obtain a tightly fit piston in a combustion chamber, machined cylinder liners are inserted into the block, one for each cylinder. A piston operates within each cylinder liner. Circulating outside the cylinder liner are the engine coolant near the top and the engine lubricant near the bottom. Thus, the cylinder liner is called a "wet sleeve liner" because it is contacted by the coolant and the lubricant. It is, of course, necessary to provide a cylinder liner seal structure to prevent intermingling of the coolant and lubricant.
In a current design, the seal structure comprises a plurality of O-rings mounted in the engine block. The engine block is machined to provide ring grooves therein, and specifically three O-rings are used at the bottom of the cylinder liner, and three more O-rings are used at the top of the cylinder liner for sealing engagement between the cylinder liner and the engine block. Each of the three O-rings is made of a different material and the O-rings are required to be installed in a predetermined sequence. A fluorocarbon co-polymer O-ring is located in the groove next to the oil, a Neoprene O-ring is utilized in the middle groove, and an ethylene-propylene co-polymer O-ring is located in the groove next to the coolant.
Since several O-ring grooves must be machined into the engine block for each cylinder, machining becomes a costly factor. Further, in the machining, it is difficult to hold required tolerances on a production basis, and tool wear and tool chatter are problems.
The present invention substantially simplifies machining of the engine block. The present invention does not require the three grooves machined in the engine block, but still enables use of the three O-ring seals at each end of the cylinder liner.
Specifically, the present invention comprises an insert which encircles the cylinder liner and has the O-rings supported therein, which engage the periphery of the cylinder liner. The insert is preferably an injection molded, high-performance plastic insert. The O-rings are received in grooves which preferably are molded into the plastic, although the grooves may be otherwise formed.
The engine block must be adapted to receive the insert which carries the O-rings. This can be readily accomplished without the extensive machining problems aforementioned. The engine block is provided with an insert-engaging surface which lies in a plane which extends transverse to the axis of the cylinder liner. On insertion of the insert into the engine block, the insert engages the surface and, thus, the insert is axially positioned relative to the cylinder liner. Further, in order to interlock the insert in the engine block, the insert is tapered, or conical in configuration, and a corresponding tapered or conical surface is formed in the engine block. The conical surface in the engine block extends from the insert-engaging surface outwardly of the engine block.